<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // Math Date RegExp Object Array String

    
    var obj = {
      uname: 'zs',
      age: 18,
      address: 'CHENGDU'
    }

    for(var key in obj) {
      // console.log( key )

      console.log( obj[key] )  // ?
    }


    // console.log( obj.age )  // 18

    // var age = 'test'
    // console.log( obj[age] )  // obj['test']  undefeind
  </script>
</body>
</html>